Field of the Invention
The present invention relates to a high-voltage coil.
Description of the Related Art
High-voltage coils to be used for power relays and switching transformers (e.g., power transformers and DC-DC converters) for electric power control and parts such as coils (e.g., coils for plug ignition) are generally used in a situation where a voltage of not lower than 100 V is applied, and an item in which a magnet wire is wound around a resin component produced by a molding method such as injection molding is used as a high-voltage coil.
When such a high-voltage coil is used for an electric system mounted around the engine of a hybrid automobile, the above-mentioned resin component is required to have a withstand voltage high enough for reducing the thickness from the viewpoint of weight reduction of automobiles and reduction in the amount of resin to be used. The resin component is also required to have a withstand voltage at temperatures not lower than 100° C. in view of the use thereof in a high temperature environment such as an engine room or the generation of heat under the application of electric current.
Heretofore, mixed compositions of a polyphenylene oxide and a polystyrene have widely been used as forming materials of high-voltage coils. Recently, the use of such materials as liquid crystalline polyesters also has been studied (see, for example, JP-A-2002-15928).
Such a high-voltage coil reaches a high temperature due to heating by the use environment or the application of electric current. Therefore, warpage or deformation may be caused if the high-voltage coil is low in rigidity in a high temperature environment. Since high voltage is applied to high-voltage coils, the reliability of a high-voltage coil may deteriorate due to the occurrence of an electrical breakdown if the coil is low in withstand voltage in a high temperature environment.
However, the above-cited patent document fails to fully disclose consideration regarding such expected problems and much room was left for studies about high-voltage coils using a liquid crystalline polyester as a forming material.